Drivers from Brighton and Hove have been warned to avoid the M23 as the motorway will be closed over lunch for emergency overhead power cable repairs.
The Highways Agency issued a warning at about noon to say that the motorway would be closed for a couple of hours. Journeys to Gatwick Airport may take longer.
The agency said: “The M23 in Surrey / West Sussex is currently closed northbound between J10 and J8 (M25), and southbound between J8 and J9 (Gatwick) for safety reasons while emergency repairs take place to overhead power cables.
“A signed diversion is in place and southbound traffic is advised to follow the hollow diamond symbol while northbound traffic should follow the solid square diversion symbol.”
Traffic apps show queues building along roads leading to the points at which the motorway is closed.
The Highways Agency said that it was working with UK Power Networks to carry out the urgent work while trying to avoid road closures affecting rush-hour traffic.